SOLVED: Still running poorly, still having vacuum issues

Linc's 200":32lljhtb said:
cfmustang":32lljhtb said:
It sounds like I have now reached the end of my abilities to solve this and will have to put the car away till I can find a actual mechanic and scrape up enough money to get it fixed.

You just need some more talented friends!!!

He has plenty of talented friends, right here at FordSix.com :D

The cam timing very well may be off, but quite frankly I wouldn't worry about it just yet, and even if it is off it still can be made to run better without spending a bunch of money. There are still several simple things to do before getting all worried about the cam.

#1) A sticky valve is not the same as a mis-adjusted valve but it can give a similar symptom on the vacuum gauge. A proper re-adjustment of the valves is definitely in order. It seems unlikely that a valve would be "sticky" on an engine this newly rebuilt but it could happen.

#2) After verifying the valve adjustment, it is time to check the timing at upper rpm's. This is where the markings on the timing pulley come into play. Just mark it at 5 degree intervals and revv it up with the timing light and tach on it. It needs to be pretty close to 35 degrees at 3000+ rpm. That is about the most that you should see with the vacuum advance unhooked. If you get 40 or more it needs to be reduced.

These are relatively simple tests, well within your abilities. Remember, you already verified the timing marks, this is no more difficult. Hang in there, you'll get it yet.
Joe
 
addo":ewsq7uql said:
a guy aka "sleeper" had an aftermarket cam that dialled 12° wrong out the box. Never say never!

Hmmmmm.....point well taken. I try not to say "never" but blanks for all major cams brands are placed in a computerised machine and they all come out perfect...usually....

I have seen some "generic brands" off by a few degrees, but I can't imagine how it is possible that a cam was ground 12 degrees off!! Where was it manufactured??
 
Lazy JW":1rqlwjb7 said:
He has plenty of talented friends, right here at FordSix.com :D

Yeah, but sometimes it is SOOOOO much easier to be there and play with it in person! :wink:
 
I kind of doubt the cam was marked incorrectly at the factory. Now whether or not the garage installed it correctly is another story.

The only reason I think that the factory marks are correct is that this is the cam my father installed when the two of us first rebuilt the engine 10 years ago. I will have to double check, but I am almost postive he did not advance the cam at all but installed it straight up per the factory marks. We never had any of the problems (cam wise) that I am having now.

What bothers me is that even at 15 degrees initial, the vacuum is somewhere around 10 hg and it is flickering up and down rapidly about 6 hg. I think the reason I can still not tune the carb is that the manifold vacuum is too low so I am having to compensate by upping the RPMs to get it to idle.

Right now, I have the idle at about 900 rpm in park. Any lower and it runs so poorly that it stalls.
 
Just to add in here, that is how I first timed my engine (All stock), turned the dizzy to the most steady reading on the gauge,@ 19 Hg. Then double checked w/ timing light, 12 degrees BTDC. Couldn't be happier, other than the engine is apart now, the turbo transformation.

Kirk ' 73 bronco
 
The problem is that it is hard to even tell what the vacuum reading is, it is fluctuating so much.

Is it the mid-point, the high-point or the low-point?

Now according to that website, a big cam (and I am assuming my 272 is a big cam) will cause a fluctuating vac reading. However, others here are getting readings around 14 and I can't even seem to break double digits. Because of this, I have to jack the idle adjustment all the way in just to get it running. If I retard the timing, it is just going to cause me to have to up the idle even more...

sigh.
 
Some vac guages are dampened some are not. The ones that are dampened are easier to read. You can try to watch the entire sweep and look for changes up or down, or a smaller fluctuation. A wildly fluctuating guage is difficult to read. The wrong mixture can cause the engine to surge and when you hit the right mixture you will see a big difference. Try to be patient, the biggest problems often bring the biggest rewards.
 
cfmustang":1oph67vz said:
.... I have to jack the idle adjustment all the way in just to get it running. If I retard the timing, it is just going to cause me to have to up the idle even more....

That's because you need more advance at idle. And also why it is important to verify your timing curve so that you can limit the centrifugal advance which will allow you to get more advance at idle and not be too much at high speed.

More advance at idle will speed up the idle, allowing you to slow down the idle by closing the butterflies, which will give you more vacuum which will allow the metering circuits in the carb to work better.

Or...... you could TRY hooking the vacuum advance to manifold vacuum, then tune the carb.
Joe
 
Joe,

I know you have recomended that before, but everything I have from Weber and about Webers says not to do that. That all say in no uncertain terms that the dizzy should use ported vacuum from the carb.

Doesn't manifold vacuum work exactly opposite of ported? Weak at idle and strong under acceleration? That should make the pinging under accelleration worse.

However, I am willing to give it a try. The only problem is that I don't have a manifold vacuum source available. The only manifold port I have is currently hooked up to the pvc valve.
 
cfmustang":3u0mjz8q said:
....Doesn't manifold vacuum work exactly opposite of ported? Weak at idle and strong under acceleration? That should make the pinging under accelleration worse.....

Nope. Manifold vacuum is highest at idle and drops toward zero as the throttle is opened which allows all the vacuum to escape. Ported vacuum is the same as manifold vacuum except at idle when the butterflies cover the ports, therefore delivering zero vacuum.

The above is NOT to be confused with venturi vacuum which DOES increase as the engine speeds up. Venturi vacuum is what the Loadamatic distributor uses. We definitely do not want venturi vacuum in your situation.

I realize that the carb makers normally recommend ported vacuum, but when an engine has a bigger than normal camyou need something to increase cylinder pressure at idle. That "something" is more spark advance, and one easy way to get it is to use manifold vacuum. LOTS of cars used manifold vacuum plus mechanical advance back in the good ol' days before emissions controls. It is not a "wrong" thing to do, and certainly is not my invention. This is an old hotrodder's trick from way back.

I suspect for very best performance you will ultimately need to have the distributor re-curved. I am just trying to come up with a short cut that will help you get to an "acceptable" level of driveability without spending a bunch of money, then when the budget allows you can make the next step.
Joe
 
Point well taken.

However, how do I use the manifold vacuum port when it is already being used by the pvc valve? Remove the pvc valve?
 
My '66 Mustang had a port on the passenger side of the intake manifold that had a threaded plug in it. I installed a hose barb and some adaptors and ran that vaccum line to the distributor.
Doug
 
Man what a thread!

Chris I admire your tenacity in both seeking help on this forum and trying the various suggestions made. Plenty (inc. myself) would have given up long ago.

Well done to those trying to help Chris, I wish I had something to offer but I'm out of my league here...

Hang in there, mate. Sounds like you're nearly there.
 
Thanks.

I wouldn't be able to do any of this without all the help I am getting here.

Sorry about the lack of updates... The budget constraints have gotten worse for the moment so I can't afford anything a the moment. I want to try adjusting the rockers and then the manifold vac to the dizzy, but I need to scrape together the cash for the valve cover gasket and the vacuum line tee (yes, it is that bad at the moment).

By the way, what kind of gasket glue is needed for valve cover gaskets (cork)?
 
I don't normally use any gasket goo for the rocker cover, but I'm no mechanic, just a fool software developer who surfs the web too much. :)

If your current gasket is fairly new and had no goo, try and reuse it. Keep an eye on it and replace if it leaks oil.

Hope the finances improve Chris, I know where you're coming from there!

Vaughano.
 
I have many valve cover gasket spares, if you can't reuse your old one I could donate one to the cause....
 
New here.new to computers.Not new to carbs. will try to help. This motor wants more air. In regard to post of june 22 mixture . This ratio of air to fuel is messed up. You are right this happens before mixture screw. Many times you have mentioned that losening idle jet holder screw letting in more air and idle improves.More air made mixture closer to correct. Idle jet sits in a mixing chamber.Fuel from main well is supplied to this chamber. Air from air horn threw a Calibrated Bushing is also supplied to this mixing chamber. Too much fuel ( high float etc) . Or not enough air (Calibrated Bushing full of dirt or blocked by wrong gasket) can mess up the ratio. More about this bushing . Can be very small and under full vacuum dirt really packs in tight.Often over looked during standard rebuild.carb cleaner and compressed air can be useless. Small stiff wire or Tip cleaners from welding supply shop may have to be used to clean bushing. Later on NO. drill bits can be used to enlarge hole if engine needs it. DO NOT do this now Location? Right above mixing chamber .May have to remove top of carb to access. Moving on . Idle jet has air holes and fuel holes to fine tune this mixture. I think you have a 70 in there now. Weber makes several different sizes.Agood idea is to have several to try out and see what motor wants.Smaller may help. Moving on weber had some carbs with idle bypass screws.This was there to create a tuneable way to let more Air in under the throttle plates. Controled vacuum leak.Would be great if the carb had one. Noticed in your posts that some times your motor responds better with a vacuum leak More air. Does your secondary throttle plate have an ajustable stop screw ? Open just slighty let in more air. If that works you could back off on your primary.And idle on your idle circuit.More on this latter.Hopes this helps.
 
Sorry for not responding for a few days.

Saturday, I pulled the valve cover (rubber gasket, yeah!) and used the How to adjust your valves instructions on the FSP website. It seemed like the machine shop over-cranked those puppies. I also replaced yet another small section of vacuum hose in the line to the AT. It seemed like I could remove it to easily. Lastly, I inserted a vacuum tee into the line that comes out of the log itself (from a brass adapter) and attached a older, but better quality gauge.

When I buttoned it all up and started it up, I seemed to run a little better but I was pulling much steadier 11 inches of vacuum. It was swinging much less, but I don't know if that was from the different gauge. I do know that that 11 Hg reading is better.

Well, getting cocky, I hooked back up the vac advance (to ported - sorry) and backed off the intial since the vacuum was advancing the inital now. When I took it for a ride, no ping, but much less power off the line. I advanced it some more till it was just starting to ping and the power was a little bit better but not where it had been when the vac advance was removed. I pulled it again and readvanced the timing. The peppiness was back, but so was the pinging. Also, all this time, the idle is still pretty shaky at lights.

It was then that I noticed a brand new problem. When idleing in gear with the brakes on, it is making a very hollow matalic rattleing noise now. I am hoping it is my exhaust rattleing under the car some where and not the tranny...
 
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